(a) Field of the Invention
The present invention relates to a zoom lens system and more specifically to a compact wide-angle zoom lens system.
(B) Description of the Prior Art
Remarkable progress has recently been made in wide-angle zoom lens systems. However, it has conventionally been considered very difficult to design wide angle zoom lens systems very compactly. The reason for it is that diameter of the front lens element is unavoidably increased, in case of zoom lens systems, in order to utilize oblique rays reaching the corners of image plane, and diameter of filter is determined according to diameter of the front lens element. Even if it is possible to minimize diameter of the front lens element, diameter of filter is increased as angle of field is widened and, therefore, outside diameter of the lens systems as completed products is still enlarged. Further, when focusing is to be preformed by the front lens group, diameter of the lens systems as completed products must be still increased taking the advancing distance for focusing into consideration so that the oblique rays will not be eclipsed. Zoom lens systems have an inherent factor to have large dimensions since airspaces are required for displacing lens groups for zooming.